Automatic welding system

ABSTRACT

An automatic weld programming system is described which is particularly suited for arc welding and in which a plurality of photocells is moved across a program sheet positioned on a console screen. The sheet contains coded indicia which cause signals to be generated to automatically control various welding parameters and synchronize various welding operations to insure that the physical welding manipulations occur in a preselected order and at a programmed rate. In addition, auxiliary system controls are also programmed so that weld environment is precisely controlled before, during and after the welding operation.

United States Patent Friedman eta].

AUTOMATIC WELDING SYSTEM lnventors: Robert Friedman, Reseda; Howard D.Lesher, Canoga Park; Richard K. Burley, Reseda, all of Calif.

Assignee: North American Aviation, Inc.

F iled: Apr. 5, 1967 Appl. N0.: 628,743

U.S.Cl ..219/125,219/l32,250/2l5, 250/235, 340/190 Field of Search..219/124-126, 131, 219/132,124 PL; 318/20.100, 20.110, 20.155, 20.300;235/151.1, 151.11; 250/202, 215, 222, 235; 340/190, 147; 228/7-9References Cited UNITED STATES PATENTS 3,005,939 10/1961 Fromer et al...318/20.l05 X Strainese et al ..340/190 X [1 1 3,657,511 [451 Apr. 18,1972 3,109,921 11/1963 Anderson ..219/125 3,126,471 3/1964 Nelson219/125 X 3,150,624 9/1964 Brems ...2l9/l25 X 3,267,251 8/1966 Anderson..219/125 Primary Examiner-J. V. Truhe Assistant Examiner-L. A.Schutzman Attorney-William R. Lane, Thomas S. MacDonald and FredrickHamann [57] ABSTRACT An automatic weld programming system is describedwhich is particularly suited for arc welding and in which a plurality ofphotocells is moved across a program sheet positioned on a consolescreen. The sheet contains coded indicia which cause signals to begenerated to automatically control various welding parameters andsynchronize various welding operations to insure that the physicalwelding manipulations occur in a preselected order and at a programmedrate. In addition, auxiliary system controls are also programmed so thatweld environment is precisely controlled before, during and after thewelding operation.

22 Claims, 19 Drawing Figures PATENTEDAPR 18 I972 INVENTORS 03597FRIEDMAN By ,e/c/m/ep K 50245-1 PATENTEDAPR 18 :972

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WWW) my mm mm wvw m 3w \vm W mm H 9% 1 AUTOMATIC WELDING SYSTEMBACKGROUND The increasingly stringent requirements and specificationsfor weld control and precision, particularly in the aerospace field,have significantly expanded the need for automatic welding equipment inwhich variations due to human errors are eliminated. In addition, theneed for consistent reproducibility of weld quality for a large varietyof alloys requires that reliance upon human skill be minimized. However,such an automatic system must be relatively simple to operate so thatsemi-skilled technicians may utilize it without affecting the quality ofthe weld produced. Further, such a system must be sufficiently versatileto allow use in a variety of welding circumstances so that the cost ofthe welding operation is not significantly increased in proportion tothe quality of the weld obtained. Prior art attempts to provide asolution to these problems have resulted in automatic curve followerswhich follow a graphic curve to control the path of a welder or othertool or welders in which only current and time sequences are programmedor in which path guidance is obtained directly from the work along withstart and stop functions. However, these prior art devices are unable toprovide precision programming of current level, weld material feed, weldfixture movement and are voltage level, all synchronized with eachother, synchronizing the weld program with the position of the arc,changing the program quickly, or providing weld reproducibility withessentially zero variations by elimination of human error.

SUMMARY OF INVENTION The present invention, particularly adapted for usein controlling a welder, is directed to an automatic programmerutilizing a removable program monitored by a photocell scanner whichgenerates a plurality of operation condition signals and a plurality ofoperating mode signals in response to the program. In the preferredembodiment a welding apparatus, including weld material feed, weldfixture moving device are voltage control, and weld heat generatingsystem, are responsive to operating mode signals to vary the materialfeed, fixture position, electrode position, and heating system operationin accordance with the program scanned. Additional synchronizing andscanning control devices are operable in response to the operatingcondition signals to insure that the scanner is moved in a prescribedmanner and at a preselected speed. In this manner an analog programmingsystem is provided in which the program may be easily modified toobviate errors in the program and which can be removed from the systemand stored for later reuse when a weld on a similar structure ormaterial is required. In addition,

' each reuse of the program will result in the controlled systemoperating in an identical manner with the previous use when the samematerials are involved. Such a system may be utilized by semi-skilledtechnicians since no experience in operating the controlled system,e.g., welding, is necessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of thesystem of the preferred embodiment of the present invention whichillustrates the principles of the invention.

FIG. 2 is a perspective view of the program and scanner utilized in FIG.1.

FIG. 3 is a drawing of a representative program sheet of reduced sizeutilized in FIG. 2.

FIG. 4 is a circuit diagram of the weld current control of FIG. 1.

FIG. 5 is a schematic diagram of the welder of FIG. 1.

FIG. 6 is a circuit diagram of the motor regulator circuit of FIG. 1.

FIG. 7 is a schematic diagram of the on-off cuit portion of the scannerof FIG. 1.

FIG. 8 is a schematic diagram of the motor controls of FIG. 1

FIG. 9 is a circuit diagram of the control circuit of FIG. 8.

FIG. 10 is a series of voltage curves for the motor of FIG. 8.

FIG. 1 1 is a series of curves showing the relationship of motor voltageand control signals of the circuit of FIG. 8.

FIG. 12 is a schematic diagram of the binary counter of FIG. I

program cir- FIG. 13 is a schematic diagram circuit of FIG. 1.

FIG. 14 is a schematic diagram of the time base logic circuit of FIG. 1.

FIG. 15 is a schematic diagram of the cycle control circuit, directionand reset circuit and manual inhibit circuits of FIG. 1

of the electrode travel logic FIG. 16 is a schematic diagram of thestepping motor logic circuit of FIG. 1.

FIG. 17 is a circuit diagram of the photocell amplifierphotovoltaic typeutilized in the system of FIG. 1.

FIG. 18 is a circuit diagram of the carriage start inhibit circuit ofFIG. 14.

FIG. 19 is a diagram of the pulse relationships at certain points of thestepping motor logic of FIG. 16.

DESCRIPTION OF PREFERRED EMBODIMENT The system of the present inventionis shown in schematic form in FIG. 1 and comprises a programming andassociated scanning means, indicated generally at 20, which generates aplurality of signals a portion of which represent preselected operatingconditions and another portion of which represent variable operatingmodes. In the specific embodiment described, i.e., an orbital arcwelding system, the variable signals utilized are weld current controland motor control, the latter control regulating the fixture rotationalspeed control and wire feed control as functions of one another. Theweld current control 21, shown in detail in FIG. 4, is responsive to oneof these variable signals to regulate the arc current supplied to thewelder, shown generally at 22 and in detail in FIG. 5. The motorregulator or decoder 23 (see FIG. 6) is also responsive to the variablesignals from the programming and scanning means 20 to govern the fixturespeed motor control 24 and wire feed motor control 25 (see FIGS. 8 and9) so that welding fixture speed and wire feed speed are synchronizedwith weld current. Each of the motor controllers 24 and 25 is responsiveto the manual control means 26 (see FIG. 15) so that wire feed andfixture speed may be manually controlled for testing, adjusting andemergency conditions. The fixture speed motor control 24 generates achain of pulses which drives a binary counter circuit 27 (see FIG. 12).These pulses are utilized by the logic means 28 and synchronize theposition of the arc welding electrode with the position of the scanningmeans relative to the program. The logic means 28 comprises the binarycounter 27, electrode travel logic means 29 (see FIG. 13), time baselogic means 30 (see FIG. 14), cycle control 31 and direction and resetcontrol 32 (see FIG. 15) and stepping motor logic 33 (see FIG. 16). Theelectrode travel logic 29 is responsive to the counter 27 and to theprogram and scanner 20 to generate an output responsive to a preselectedoperating condition which defines the electrode travel scale in terms ofdegrees. The time base logic 30 is responsive to the output of theelectrode travel logic 29 and to the program and scanner 20, to generatea signal representing a selection of the electrode travel base, i.e.,degrees of rotation or seconds of time, to drive the stepping motorlogic 33. The stepping motor logic 33 is responsive to the cycle control31, to the direction control 32 and time base logic 30 to drive astepping motor 34. The stepping motor 34 physically drives the scanneracross the program as shown in FIG. 2.

The specific circuits shown diagrammatically in FIG. 1 will be describedin detail with respect to FIGS. 2-19. The pro-- 5 gramming and scanningmeans '20 is shown in perspective view in FIG. 2 and comprises atransparent table 35, illuminated from beneath, upon which a removableMylar sheet or program 38 is placed. The program 38 contains indicia, orhas them removably attached to its surface, which indicia define theinterrelationship of the variable parameters of the process beingprogrammed. A carriage 36 carrying a plurality of indicia detectors,e.g., photocells, is adapted to move across the program and scan theindicia thereby monitoring the program.

In addition, a plurality of fixed photocells 37 are responsive to 1indicia located on the right hand side of the program 38.

The Mylar sheet is shown in detail in FIG. 3 and comprises three mainareas. The lower area 40 is adapted to carry a graphic representation,preferably by placing opaque tape in a configuration representing thedesired variation in the welding current as a function of time orelectrode travel. The upper graph area 41, located above the area 40, isadapted to carry a second such graphic representation of the desiredinterrelationship of the fixture speed and wire speed variations withinthe ranges A through E and A through G, shown on the left and right handsides of area 41, respectively. The selection of the particular range isaccomplished by introducing opaque indicia on one of the plurality ofappropriate lettered squares in areas 45 and 46. Similar selections aremade for other variables identified in areas 42 through 47 on the righthand side of the program 38. In addition, on-off control for fixtureoscillation 48, wire feed 49, electrode travel 50 and program limit 51are provided at the top of the program. Each of the graphicrepresentations, the selection of ranges or the on-off control which maybe specified on the program are selected by means of placing opaque tapein the proper position. The programmer has a plurality of fixedphotocells 37, one under each of the lettered squares on the program 38adjacent areas 42-47, which sense whether the various indicia receivingsquares have been covered. In response to the presence of these programindicia, as indicated by the monitoring scanner 20 or the fixed monitors37, an appropriate signal is generated representing the programmed valueof each of the operating parameters which control the operatingconditions of the process. After the various program area indicia havebeen found to produce a satisfactory weld, a permanent copy may be madefor future welding use. In this manner the operator would be unable tochange the weld program and weld uniformity could not be affected. Thecarriage 36 of the scanning means 20 is composed of a vertical armcarrying 100 photocells which read the information from the lower area40, forty additional photocells which scan area 41 of the program, andfour photocells one of which scans each of the associated areas 48-51for on-off control. While opaque tape and photocells are used in thepreferred embodiment, other types of indicia and detectors may be used,for example, magnetic indicia and interacting detectors.

Photocell Amplifiers The photocells used in detecting the program,represented by opaque tape 52, in areas 40 and 41 utilize photocellamplifiers particularly adapted for use with the voltaic type photocell.These units are shown in detail in FIG. 17 and have a l .5 v. supplyconnected to the high side of photocell 53 so that upon exposure tolight the current output turns on the transistor. This shunts thecollector voltage on the transistor to ground and results in an outputequal to zero. In the unit of FIG. 17 anytime the transistor is in anon-conducting state because no light is present on the photocell 53,the resistors R and R form a voltage divider. In the circuits in whichthese units are used, 100 for the scanner portion covering area 40, theoutput is connected through a diode to form an AND gate. In this mannerthe voltage appearing at the common connecting point 54 from thephotocell array (see FIG. 4) will be the voltage output of the photocellhaving the greatest output. This is apparent if it is considered that iftwo photocells are turned on, i.e., illuminated, the voltage appearingon the common points will be the higher of the two outputs, since anyoutput lower than the highest will cause the output diode to be numberof these units may be connected in this manner and the output will bethe highest voltage of the photocells which is not receiving light. As aresult of this photocell arrange ment, the program indicia, indicatedgenerally at 52, used on the areas 40 and 41 need only be opaque tape afraction of an inch wide, the configuration of which will define therelationship between the variables of the horizontal and verticalprogram axes for the particular program area.

Weld Current Control The common point output 54 is connected to the weldcurrent control 21 shown in detail in FIG. 4. The output 54 is connectedto the input of a standard constant current circuit 55. This in effectties the voltage at this point to the output of the photocell array. Theload of the constant current circuit is a voltage divider circuitconsisting of a pair of variable resistors 56 and 57 each connected inseries with a control relay 58 and 59. The selection of which of theresistive values 56 or 57 is to be used is through the use of an opaqueindicia covering one of the fixed photocell squares in area 42 of FIG.3. This selection determines which of the current scales on the leftside of area 40 is to be applicable during the particular program. Theoutput 60 of the weld current control circuit is a voltage which isdetermined directly by the single photocell of the highest outputcircuit voltage which in turn is responsive to the location of theopaque programming tape in area 40.

Welder The output 60 of the weld current control circuit is connected tothe input of a welding means 22, comprising a closed loop controlsystem, shown in more detail in FIG. 5, which generates an output whichis a direct linear function of the input signal at 60. Since allelements of the welding means are standard, only the general arrangementwill be discussed. The control loop comprises a weld current supply 61having shunt 62 in series with the load. The current in the shunt isdetected by a chopper 63, and amplified and subtracted from the inputsignal 60 by amplifier integrator 64 to generate an error voltage. Theerror voltage is then amplified and conditioned to properly drive an SCRcircuit 65 which controls the power supply 61. More specifically, thechopper circuit 63 comprises a fixed frequency unitrode relaxationoscillator of standard design which drives a standard inverter. Theoutput of the inverter drives a binary input to a standard flip flopcircuit which in turn drives an emitter follower. The output of theemitter follower drives the chopper circuit which consists of a solidstate device which switches the input to ground to a frequency fixed bythe driving relaxation oscillator. The output of the chopper circuit 63is a square wave signal having an amplitude directly proportional to thewelding current being generated by supply 61. This square wave is fedinto an LRC filter circuit which is tuned to pass only the fundamentalfrequency component of the square wave. This filtered signal drives apushpull a.c. amplifier the output of which is demodulated to provide adc. signal proportional to current. This demodulated signal issubtracted algebraically from the command signal at input 60 to providean error signal representing the difference between the desired currentindicated on the program 38 and the actual current detected at the shunt62. This signal drives a standard emitter follower isolation circuitwhich is connected to a differential input amplifier 66. The output ofamplifier 6 drives a voltage level shift circuit of standard designwhich is used to bias the base of the unijunction transistor in the SCRfiring circuit 65. The SCR firing circuit, which may also be standard,detects the conditioned error signal and controls the silicon controlledrectifier in the weld current supply 61. The weld current power supply61 is standard and comprises primarily a full wave bridge with siliconcontrolled rectifier forming the positive voltage leg. When the SCRs areturned on, the conducting SCR remains conducting until the voltageacross the element drops to zero. In this manner changing the firingangle will result in a corresponding change in the current to the load.

In the case of an arc welding operation it is essential that thereversed biased and therefore nonconducting. Thus, any arc be startedand after start be maintained in a stable manner.

The are starter 67 may be a standard circuit utilizing a combination ofa high frequency circuit and a high voltage arc stabilizing circuit, theformer initiating the arc and the latter heating the electrode andmaintaining a residual current within the system. The starter 67utilizes a diode bridge to monitor the open circuit voltage output ofthe supply 61. When that voltage reaches a prescribed range, e.g.,80-100 v., the arc is initiated. Once the arc is initiated the highfrequency is turned off and the are maintained by the high voltage arestabilizing circuit 67. In this manner the to the work 68 and thecurrent utilized is controlled by the indicia in area 40 on the program38 scanned by the photocells on the carriage 36.

Motor Regulator The carriage also contains an additional series of fortyphotocells which are used to scan area 41 of the program 38. Thesephotocells are connected in the same manner as discussed above. As aresult the voltage output of the second array is the most negative ofthe cells which is not receiving light through the program sheet 38because of the presence of opaque indicia 52. This voltage is fed to thecollector of the input transistor of a standard constant current circuit70 in the motor regulating circuit 23, shown in detail in FIG. 6. Theload on the constant current circuit 70 is a transistor connected in anemitter follower arrangement 71 such that the base of the transistor isheld at a constant level by circuit 70 and is set at a level such thatthe transistor remains conducting, as is well-known in the art. Theoutput of the emitter follower 71 is connected through a voltage dividercircuit, indicated generally at 72, to the wire feed motor control 25.

The constant current circuit 70 is also connected through a voltagedivider circuit, indicated generally at 74, to the fixture speed motorcontrol 24. The program 38 (see FIG. 3) provides an area 45 in which thefixture speed range may be selected by placing an opaque indicia overone of the appropriate squares A-E adjacent area 45. The precise rangesavailable for selection are shown at the left side of area 41 on program38. Each of the squares A-E of area 45 has an associated fixed photocellwhich, when not exposed to light from the table 37, results in theclosing of a control relay. The control relays 76-80 in FIG. 6 areassociated with the fixed photocell areas A-E of area 45. One of therelays 76-80 is closed by the preselection of fixture speed range byplacing an opaque indicia over an appropriate control condition definingsquare. This connects one of the variable resistors 81-85 between theoutput of the constant current circuit 70 and ground so that the voltageinput from the photocells into circuit 70 is reflected as a variablecurrent at the input of motor control 24.

In a similar manner the voltage divider circuit 72 is composed of sevenrelays 87-93 and seven variable resistors 94-100. The relays 87-93 areresponsive to the placement of an opaque indicia in one of the sevensquares A-G adjacent area 46 on the program 38 (see FIG. 3). The rangesof wire speed available are indicated at the right side of program area41. The wire feed rate and fixture speed rate are clearly related sincethe faster the welding fixture is moved the faster the wire must be fedinto the arc to accomplish the welding. Further, the speed of these twoelements may require relative variation to accommodate changes in thethickness of the material to be welded. Thus, the ranges provided ineach instance allow considerable discretion. It is clear that, ifdesired, the on-off program areas adjacent areas 48-51 on the programcould be used to change the preselection from one range to anotherduring operation if desired.

A plurality of individual scanning photocells 105-108 (see FIG. 7) areprovided on the carriage 36, one each for each program area 48-51. Eachresistive type photocell 105-108 has an associated amplifier 109-112which has a high effective resistance. The amplifiers are of standarddesign and operation, and control the respective relay controls 113-115for photocells 105-108, while the output 116 of the program limitphotocell 108 associated with area 51 is connected to the cycle controlcircuit (see FIG. 11).

welding arc is applied Thus, as the carriage 36 is moved across the faceof the pro gram 38 which is illuminated from beneath, the photocells-108 will generate signals in response to the presence of opaque indiciastrategically placed in the various program areas 48-51. The cooperativeoperation of these individual scanning means with respect to theremainder of the circuits will be more apparent in the hereinafterdescribed operation of the system.

Motor Control Circuits Two separate motor control circuits 24 and 25 areused although they are identical in all essential respects. Such acircuit is shown in schematic form in FIG. 8 and in detail in FIG. 9.Each of the two motor control circuits 24 and 25 drive individual shuntwound motors 117 utilizing a 48 v. d.c. supply 118 in the preferredembodiment. Attached to the shaft of the motor is a slotted wheel whichmakes and breaks a light path to a photosensitive silicon controlledrectifier which is used to control the operating speed of the motor asshown diagrammatically at 119. The motor control circuit 120 is shown indetail in FIG. 9 and is composed of an input section 121, a constantcurrent source 122, an unijunction pulse generator 123, an over-speedcontrol circuit 124, a speed indicating circuit and a motor drive stage126. This system is of the switching mode variety in which a transistorswitch is placed on the ground side of the motor and which drives themotor with pulses. Considering the motor and switch isolated from therest of the circuit of FIG. 9 and assuming a source of appropriate motordriving pulses, when the transistor 143 is turned on the voltage drivesthe motor at maximum speed. FIG. 10 illustrates the voltage timerelationships for various speeds. The longer the voltage is applied tothe motor relative to the off period of the cycle, the faster the motorwill travel. Curve 128 shows the application of the voltage supplyoutput during the entire time and results in maximum motor speed. Curves129, 130 and 131 show a decreasing time of voltage application andresult in high, medium and low speed motor operation, respectively.Thus, the pulse width controls the motor speed.

In general the motor controls 24 and 25 maintain the speed of theirrespective motors at a constant rate regardless of the motor shaft load.Both underspeed and overspeed compensation is provided to permit a rapidreturn of the motor to the desired speed upon load changes.

FIG. 11 illustrates the voltage wave shapes of the motor voltage pulsecurves 132, unijunction oscillator emitter voltage curves 134, thevoltage output pulse 133 resulting from the operation of the slotteddisc, and the change in load curve 135 causing the various changes involtage. During the time illustrated between points 136 and 137 astandard speed operation is depicted. The motor is turned on at thenegative slope position of the sawtooth 134 and turns off at the timethe output 133 is generated by the disc and light source 119. Curve 132shows the pulses applied to the motor. If at point 137 the load isincreased the emitter of the unijunction 143 (see FIG.

9) of the unijunction pulse generator 123 charges at the usual slope tothe point where it is clamped at a voltage value less than the valuerequired for firing. Thus, the voltage remains on the motor until thenext pulse 139 is received from the speed control 119. When this pulseis received the voltage to the motor and the voltage clamp are removedresulting in the firing of the unijunction which in turn reapplies thevoltage to the motor. This continues as indicated during the time period137-138 until the sawtooth voltage fails to reach the clamping voltagev, associated with curve 134, before the pulse 133 is received. Point140 of curve 134 illustrates the return to proper speed of the motor. Inthis manner underspeed conpensation is attained.

If at point 138 the load is suddenly reduced the momentum of the motorwill result in an overspeed condition. In this condition the motor isprevented from turning on until the voltage on the emitter of transistor142 reaches the normal triggering level of the unijunction.

Referring now to FIG. 9, an example of the motor control circuits 24 and25 is shown. The input section receives a signal over lead 127 from thevoltage divider 72 or 74 (see FIG. 6).

The input section 121 is connected to a constant current section 122, ofstandard design, the output of which is connected to one side ofcapacitance 141 and the collector of transistor 142 of the unijunctionpulse generator or transistor relaxation oscillator. This circuit 123uses the constant current capacitor 141 which will start charging when aconstant current is applied. When the voltage on the emitter oftransistor 143 reaches a particular voltage, the device conducts betweenpoints 144 and 145. As a result transistor 142 is turned on, shuntingthe emitter of the unijunction transistor 143 to ground. In this mannerthe device is reset permitting the cycle to start again. Transistor 142provides a discharge path for condensor 141 so that the dischargecurrent does not pass through the emitter of transistor 143. Since thevoltage change takes a finite time the low side of capacitor 141 goesnegative and a negative pulse is applied through capacitor 146 tomomentarily turn off transistor 147. As a result a positive pulse isapplied through capacitor 148 to gate the silicon control rectifier 149.

The SCR 149 is a part of the motor drive circuit 126. If a positivepulse appears on lead 150 the SCR 149 turns on applying a positive biasto transistor 151 and in turn to transistor 152. A positive bias appliedto the base of transistor 151 results in the motor winding connected tolead 153 from the collector of transistor 151 being grounded through thetransistor. In addition, the positive bias applied to the base oftransistor 152 inhibits the overspeed circuit 124 through lead 154 anddiode 155. The circuit remains on until the anode of the SCR 149 isgrounded through lead 156 by the speed indicating circuit 125.

The speed indicating circuit utilizes a photosensitive silicon rectifier160 which is responsive to either light or a gating current. In thiscircuit the transistor 161 is used to charge the capacitor 162. When nolight reaches the SCR 160 the capacitor 162 is charged throughtransistor 161 and resistor 163. The effective resistance allowscapacitor 162 to charge quickly turning off transistor 164. When lightreaches the SCR 160 it is turned on and capacitor 162 discharges throughdiode 165 and the SCR circuit. The firing of the SCR 160 turns ontransistor 166 which, through lead 156, turns off the SCR 149 in themotor drive circuit. 126. Also when capacitor 162 discharges, transistor164 turns off permitting a pulse to be applied over lead 167 to theoverspeed circuit 124.

In this manner if a pulse is received from the pulse generator 123 themotor connected to lead 153 is turned on. As soon as the light hits thephotosensitive SCR 160 the motor is turned off.

Underspeed control is accomplished by placing a clamp on the emitter 145of unijunction transistor 143 of pulse generator 123. This clamp isoperable whenever the voltage is being applied to the motor. Since thevoltage level is just less than the triggering voltage of theunijunction 143, the capacitor 141 can only charge up to that value andtherefore transistor 143 will not trigger. This permits the pulsegenerator 123 to generate a pulse at the output essentiallyinstantaneously after the motor control SCR 149 is turned off, and turnsthe motor back on to let it reach desired speed more rapidly. Thisoperation requires that the charging current to capacitor 141 be of sucha value that it is charged to the clamping voltage prior to the timethat a pulse is received from the speed indicating circuit 125 turningoff the motor and clamping voltage.

Overspeed control is provided by utilizing transistor 180. Thetransistor, when turned on, energizes transistor 147 so that it will notturn off from a pulse from the unijunction transistor 143, and alsoreduces the voltage on base 2," 181, of the transistor 143. As a resultthe firing voltage of transistor 143 is lowered. This voltage issufficiently low, however, so that transistor 147 is not thereby turned011. When transistor 147 is turned off the pulse generator 123 mustagain start its charging cycle. Assuming the motor is running from aprevious pulse and the SCR 160 turns off the motor, the turning off theturning off of the motor control SCR 149 and the pulse duration fromtransistor 164 so that the transistor 180 remains off. If another pulseis received from the photosensitive SCR 160 before the next pulse isgenerated by 123, this pulse will reset the unijunction transistor inthe manner described above. The motor is thereby allowed to slow downthrough an extra cycle before it is again energized. This operation willbe repeated until the pulse from the generator 123 is received be forethe next pulse from the SCR 160 at which time the motor has slowed tothe desired speed.

By utilizing such a motor control circuit very precise control isachieved over the fixture movement and wire feed of the welder. Suchprecise control is essential in order to synchronize all weld operationswith the weld current variation and electrode travel movementsprogrammed.

Pulse Generator The fixture speed motor control 24 (FIG. 9) provides apulse output at 182 equivalent to about 160 pulses per degree of weldfixture head motion. This pulse source is used through binary counter27, electrode travel logic 29, time base logic 30 and stepping motorlogic 33 to drive a stepping motor 34. The stepping motor 34 drives thecarriage 36 across the program and is preferably set so that about 5000pulses will move the carriage across the entire area 40. In thepreferred embodiment each pulse moves the carriage 0.005 inch or 200pulses are required per inch of carriage travel. Thus, if scale A inarea 44 (FIG. 3) of the program 38 is selected the horizontal programscale will be 500 degrees and the pulse output of the motor must bedivided by 16 to give full scale carriage movement. In a similar manner,scale B, C and D, i.e., 1000, 1500 and 2000 degrees electrode travel,can be achieved by dividing the pulse rate by 32, 48 and 64,respectively. This scaling down by the appropriate amount isaccomplished in the binary counter 27, shown in detail in FIG. 12. Thebinary counter utilizes six standard flip flop circuits 217-222connected in series. The pulse train output 182 of the fixture speedmotor control 24 is connected to the input of an inverter 223 (FIG. 12)which drives flip flops 217-222. Each of the inputs of flip flops218-222 are connected through diodes to a reset signal and cycle controlinput 224, the purpose of which will be apparent from the discussion ofthose circuits. The outputs of flip flops 220, 221 and 222 correspond toevery 16, 32 and 64 pulses, respectively, at the input at 223. Ifdivision by 48 is desired the system is altered to generate an outputfrom flip flop 221 every 48 counts. This is accomplished through the useof a NAND gate 225. The NAND gate 225 is operated by an input signalthrough lead 226 from electrode travel logic circuit 29, as described indetail hereinafter. The other inputs, 227, 228 and 229 to the NAND gate225 are the output of the divide by eight flip flop 220 and thesecondary outputs of the divide by 32 and 64 flip flops 221 and 222,respectively. In this manner an extra 16 counts are added to the flipflop 221 every time flip flops 219, 221 and 222 generate an output,provided the NAND gate 225 is operative. Thus, the flip flop 222 ischanged from a divide by 64 to a divide by 48 flip flop. The threeoutputs 230, 231 and 232 of the binary counter 27 are connected to theelectrode travel logic circuit 29, shown in detail in FIG. 13.

Electrode Travel Logic The electrode travel logic shown in detail inFIG. 13 comprises four resistive type photocells 235-238 which arephysically fixed above the spaces A-D adjacent area 44 on the program 38of FIG. 3. Each photocell has an associated amplifier 239-242 theoutputs of which are connected through inverters to the inputs of ANDgates 243-246. If none of the scales are selected, i.e., none of thephotocells 235-238 are covered and therefore none of the gates 243-246are turned on, the carriage operation is controlled solely by the timebase logic circuit 30 (FIG. 14). Ifone of the electrode travel scalesadjacent area 44 of program 38 is selected'then one of the AND gates243-246 will be operative to pass the pulse signals on one of the leads230-232 from the binary counter to the NOR circuit 247 which isconnected through an inverter to output lead of the motor and theturning on of transistor 164 are timed by 248.

The outputs of amplifiers 239-242 are also connected to a NAND circuit249 used as an AND circuit with several inputs. In this arrangement thegrounding of any of the inputs will result in the generation of anoutput signal at lead 250. Thus, a signal at 250 indicates that one ofthe operating conditions A-D has been preselected on the program.

Time Base Logic The time base logic circuit 30 is shown in detail inFIG. 14 and has a single photocell 253 connected through a standardamplifier 255 to a time base generator 256, and an input 254 fromelectrode travel photocell 107 (see FIG. 7) connected through a standardamplifier 257 and inverter 258 to a NAND circuit 259. The purpose ofthis circuit arrangement is to control the motion of the photocellcarriage 36. This is accomplished through the output of the AND gate 260which is connected through a NOR gate 261 and inverter 262 to output 263to the stepping motor logic circuit 33.

The AND gate 260 generates an output only if l) the carriage motion isforward, i.e., left to right, (2) the carriage start circuit is true,and (3) the electrode travel-on is true. The input at 254 from electrodetravel photocell 107 determines condition (3), while the input from thecarriage start inhibit circuit 268 determines condition (2). Thecarriage motion condition (1) is determined by the input on lead 269from the direction and reset circuit 32 (see FIG. 11).

Assuming these three conditions have been met a chain of pulses isgenerated by the time base generator 256, i.e., a standard pulsegenerator the pulse rate of which is controlled by photocell 253. Thepulse generator 256 generates 66% pulses/sec. when the photocell 253,which is under square in area 43 of program 38, is not covered. If A iscovered, there being no photocell under indicia receiving square A inarea 43 of program 38, the result is the same as when square B is notcovered. If square B is covered so that no light reaches the photocell253 the oscillator pulse rate is 33% pulses/sec. This selection allowseither the 75 second or 150 second basic speed shown on the horizontaltime scales on the bottom of the program.

The carriage start circuit 268 must have a true reading before thecarriage 36 will start scanning the program 38. The purpose of thiscircuit is to determine if the an arc has occurred between the weldingtorch and the work 68. The input 267 from the arc starter circuit 67indicates the condition of the welding arc. The voltage from the arcstarter 67 has the characteristic of being high before the arc isstarted and dropping to a lower voltage after arc initiation. Thisvoltage is a negative dc. voltage and is applied to the carriage startinhibit circuit 268 shown in detail in FIG. 18. When this negative inputsignal from 67 is higher than the breakdown voltage of the zener diode270 the base voltage of transistor 271 goes negative turning off thecurrent flow through 271. This provides a true signal output at 267stopping the carriage from moving. Once the arc has been initiated thesensing voltage drops to below the breakdown voltage of the zener 270and transistor 271 turns on giving a false signal to the inverter 273and a true signal to both AND gates 260 and 275.

Another condition which must be met in order to obtain an output fromAND gate 260 is that the direction flip flop 276 (see FIG. 15) in thedirection and reset circuit 32 indicates that the carriage will move inthe proper direction. The output of direction circuit 276 indicates areverse direction until the pre-purge delay 277 has dropped out, asexplained in detail hereinafter. When delay 277 has dropped out, flipflop 276 is switched and the output on lead 269 permits the carriagemotion to start if all other conditions have been met.

Referring again to FIG. 14, when lead 278 is true, the output of gate260 is eliminated and the output of gate 275 is made possible, since thetrue signal on 278 is inverted at 279 and then applied to gate 275.Thus, when gate 260 is closed either gate 275 or gate 280 controls theoutput at 263.

When gate 275 is operating the output at 263 is a function of degrees ofweld head motion rather than time, i.e., the signal is determined by theselection of electrode travel range by means of photocells 235-238 ofthe electrode travel logic 29 through lead 248. As eirplained above,four horizontal scales (bottom of program 38) in degrees are provided.If none of the scales A-D of area 44 are selected, i.e., photocells235-238 are all uncovered, the input to AND gate 260 is automaticallytrue regardless of the condition of the electrode travel on photocell107. This results in the carriage operating on the time base since gate275 is turned off. If one of the electrode travel scales A-D of area 44is selected the condition of both gates 260 and 275 is governed by thephotocell 107 and the signal on lead 254. Since the signal on leads 278and 279 are opposite only one of gates 260 and 275 is operable at atime.

Gate 280 is responsive to the direction and reset circuit 32 throughlead 281 and the cycle control circuit 31 through lead 282. The gate 280is connected to rapid return pulse generator 283 which is connectedthrough gate 280 to the stepping motor logic circuit 33 only when theproper signals are present on both leads 282 and 281. The generator 283drives the carriage 36 back across the program in response to the changein signals from direction flip flop 276 through lead 281 and a closedcycle start switch 283 (see FIG. 15 When the carriage is returned to thestarting position switch 284 in the cycle control circuit 31 is closedand gate 280 is grounded.

Cycle Control, Direction and Reset, Manual Control Circuits The cyclecontrol circuit 31, direction and reset circuit 32 and manual controlcircuit 26 are shown in detail in FIG. 15. These circuits providebuiltin safety circuits, automatic logic circuit pre-set, automaticpre-purge, automatic weld sequencing and automatic shut down and postpurge. The cycle control 31 has an input 116 from limit photocell 108(see FIG. 7) which is associated with area 51 of program 38 whichgenerates a signal when the program indicated in areas 40 and 41 isended.

A water flow switch 286 by-passes the cycle stop switch 287 and preventsthe system from starting unless actual coolant flow exists in the weldhead. This is accomplished byholding the forward direction output signalon lead 269 of direction flip flop 276 false.

A left-hand carriage position switch 284 is wired in series with thestart switch 283 thereby preventing cycle start until the limit switch284 is closed. A right hand limit switch 288 is also provided whichautomatically shuts the system down when the carriage reaches thispoint. Upon turning on the power the voltage at 289 pre-sets thedirection 276, pre-purge delay 277, cycle start 290 and post purge delay291 flip flops. Upon closing the cycle start switch 283 the binarycounter 27 is pre-set to zero through lead 224 and the pre-purge delaytime 277 is initiated. This also causes the output 292 of cycle startflip flop 290 to go false. This signal is inverted at 293 and operatesrelay 294 which turns on the purge gas supply to prepare the weldenvironment. The output 292 is also inverted at 295 to remove thevoltage previously available through lead 296 to manual control wirefeed switch 297 and electrode travel switch 298. In this manner themanual feeding of wire or the manual movement of the electrode isprevented after the cycle start switch has been energized. The output ofinverter 299 goes true and also starts the pre-purge delay timer 277. Atthis time the output of inverter 301 inhibits the post purge delay timer291 from operating. After a pre-selected delay the pre-purge delay 277operates to switch both the timer flip flop 300 and direction flip flop276 by grounding the output 302 of timer 300 and the output 281 of thedirection flip flop 276. The timer 300 by means of inverter 303 inhibitsthe pre-purge timer 277 from recycling. In addition, the output of thepost purge delay 291 is inhibited by the output of inverter 304.

The pre-purge and post purge delay circuits 277 and 291 have a pair ofphotocells 305 and 306 and associated amplifiers 307 and 308 connectedto their inputs. These resistive photocells are located in area 47 ofthe program 38 and are utilized to preselect the amount of purge time byplacing indicia over square A or Bof area 47.

The cycle stop switch 287 is connected through inverter 309 so thatvoltage from source 310 is applied to control relay 311 to apply powerto the weld power supply 61. The relay 311 has normally open contacts312 and 313, the fonner controlling voltage to the weld head oscillatormotor 314 and the other connecting voltage supply 315 to the wire feedmotor 316 and electrode travel motor 317. Relay contacts 318, 320, 325and 327, which are normally closed, and contacts 319, 321, 323 and 324,which are normally open, are responsive to control relay 328. Controlrelay 328 is operative in response to the closing to position A or B ofeither manual electrode travel switch 297 or manual wire feed switch298. In both cases the switch is used to position the electrode or theweld wire before automatic operation begins. Contacts 322, 326 and 332are nonnally open and are controlled by relays 113, 114 and 115,respectively, of FIG. 7 which in turn are responsive to photocells105,106 and 107 which scan areas 48, 49 and 50, respectively, or program38.

When switch 298 is in either position A or B the control relay 328 isactivated resulting in contacts 318, 320, 325 and 327 being opened andcontacts 319, 321, 323 and 324 being closed. When contacts 171-172 and173-174 are connected by switch 298 the voltage polarity on wire feedmotor 316 is reversed from that of position 175-176 and 177-178 to allowproper initial positioning. In a similar manner when contacts 183-184and 187-188 are connected by switch 297 the voltage polarity on theelectrode travel motor 317 is reversed from that when 185-186 and189-190 are connected.

Output leads 330 and 331 corresponding to the output 153 of the motorcontrol circuit (see FIG. 9) are provided for each of the wire feed andfixture speed motors. The wire feed motor 316 during welding operationis isolated by open contacts 319, 321, 313 and 324 (all on control relay328) from the switches 297-298 and is isolated from the motor controlcircuit of FIG. 9 only by contact 326. Relay contact 326 is controlledby relay 114 which will be closed as soon as the photocell 106 (see FIG.7) indicates the presence of an indicia in the area 49 of FIG. 3. In asimilar manner the electrode travel motor 317 is isolated from thecontrol circuit of FIG. 9 by contact 332 which is controlled by relay115 (see FIG. 7). Relay contact 332 is normally open and will close whenindicia is detected by photocell 107 in the area 50 of the program ofFIG. 3. The weld head oscillator motor 314 is similarly isolated from avoltage supply 310 by contacts 312 and 322. Contact 312 is closed bycontrol relay 294 while contact 322 is closed by relay 113 in responseto the presence of indicia in area 48 being detected by photocell 105.

Stepping Motor Logic The stepping motor logic circuit is shown in detailin FIG. 16 together with the windings of the stepping motor 34 whichdrives the carriage 36 across the program 38. The carriage 36 iscomposed of a vertical bar containing photocells as described in detailabove and must move across the program in a precise manner so that thecorrect motor speeds and weld currents are provided to the welder at theproper time or at the proper angular position of the electrode. Itshould be noted, however, that it is within the purview of the presentinvention to move all or portions of the program with respect to theindicia detectors if desired.

Thus, the carriage may be operated in either the time base operatingmode through gate 260 of the time base logic circuit 30, FIG. 14, or inthe degree or rotational travel operating mode through gate 275. Ineither event the output at 263 is a series of pulses either time basedor degree based.

The carriage position is controlled by the stepping motor 34 which hasits output geared such that 200 steps is equal to one inch of travel.Internally the motor has four operating coils 352-355 which, when pulsedin preselected sequence, will control the direction of motor rotationand carriage travel. The speed of the motor is a function of the pulsefrequency at 263. The stepping motor logic circuit of FIG. 16 controlsthe sequence of applying these pulses to the motor coils.

The logic circuit 33 converts the input series of pulses into separatepulse commands for each motor coil. These motor pulses are phased sothat the motor 34 will rotate 1.8 degress for each input pulse. Thus,200 steps are required for one resolution of the motor 34.

Flip flops 334 and 335 are connected as binary counters to providedivide by 2 outputs at 336 and 337 and divide by four outputs at 338 and339. The outputs are connected to a series of eight gates 340-347 so asto provide four separate outputs. Each output comprises a train ofpulses which are inverted and current amplified into pulse commands atpoints 348-351 to step the motor sequentially. The outputs 269 and 281of the direction flip flop 276 of the direction and reset circuit ofFIG. 15 are connected to gate 345, 347 and 344, 346, respectively, toalter the pulse command sequences to provide both clockwise and counterclockwise rotation of the stepping motor 34.

FIG. 19 shows the pulse levels at points 263, 336-339 and 348-351 onFIG. 16. Points 348-351 reflect the pulse commands to the coils 352-355.In all cases zero volts to the coil is a clockwise direction thatrelationship between the steps 1-4 and the point 348-351 is as shown inTable I.

TABLE I Points Step 348 349 350 351 l on off off on 2 off on off on 3off on on off 4 on off on off 1 on of! off on The time sequences atpoints 348-351 for reverse travel are the same as shown in FIG. 19except that the voltage levels at points 350 and 351 are interchanged.In the case of reverse logic, counter clockwise direction Table II showsthe step and point relationship.

TABLE II Points Step 348 349 350 351 l on off on off 2 off on on off 3off on off on 4 on off off on 1 on off on off In this manner thestepping motor is precisely controlled so that the actual weldingcurrent, fixture speed and wire speed correspond to that programmed onprogram 38 at each point along the horizontal scale whether the selectedscale degrees of electrode rotation for cylinder welding or seconds oftime.

OPERATION In operation a program 38 (see FIG. 3) is positioned in apreset relation on the illuminated glass table 35. Ordinarily theprogram will have a current vs. degree (or time) curve 191 in area 40, afixture speed-wire speed curve 192 in area 41, and various indicia193-196 associated with on-off program areas 48-51. In addition, controlconditions will have been selected by placing indicia over appropriatesquares associated with areas 42-47. In the particular programillustrated in FIG. 3, the current scale B, at 197 and providing a rangeof 0-150 amps, is selected. Placing an indicia over current scaleselecting square B results in control relay 58 (FIG. 4) being energizedso the resistor 50 is placed in the load of constant current device 55.In this manner the weld power supply,'FlG. 5, is preset to provide theselected range of amperages to the are.

No electrode time base was selected in area 43, however, the circuitautomatically starts operating on the second time base. The carriagemust always be started on time base operation and may then be changed toelectrode travel base operation only after the initiation of theelectrode travel motor by indicia 195 in area 50 of the program. At thattime operation on the time base is terminated and the electrode travelbase is operative to control the system.

Thus, square B at 198 is covered resulting in the 1-1000 degree rangebeing selected and in the generation of an output from amplifier 241,FIG. 13. This output will energize gate 245 so that pulse signals onlead 231 from the binary counter 27 will be applied through lead 243 tothe stepping motor logic input at 263 (FIG. 16). It should also be notedthat since an output will be generated at 250 (FIG. 13) the output ofNAND 259 (FIG. 14) will disable gates 260 so that the only signalapplied to NOR gate 261 will be the output of the electrode travel logiccircuit at 248. The fixture speed and wire speed selection are made asat 199 and 200. In this case the range selections l.6 rpm and 0-l2.4in/min., respectively, allow a straight program indicia 192 to beutilized. Placing opaque indicia over fixture speed selecting square 199results in control relay 78 (FIG. 6) operating to connect resistance 83as the load on constant current source 70 so that a signal is applied tomotor control 24 representing this selection. Similarly, placing opaqueindicia over wire feed square 200 results in control relay 92 connectingresistance 99 between the output of 71 and ground so that a signal isapplied to wire feed motor control representing this selection. Purgetime square A, 201 representing a second purge time, is selected therebycausing an output to be generated by amplifier 307, FIG. 15, which setsthe delays 277 and 291.

Assuming the system has been reset and that the carriage is in the lefthand position, start switch 283 (FIG. is closed and the output on lead292 of cycle start flip flop 290 starts the prepurge cycle as explainedabove and the binary counter is reset and the carriage will start tomove.

As the carriage 36 starts to move across the program the curve 191 todetected by an array of photocells and the signal at 54 (see FIG. 4)changes in response to the location of the opaque indicia. This signalis applied to the welder which is responsive to increase the currentuntil it reaches a value of about 100 amps. Note that no weldingoperations have yet taken place in this example. At the time of maximumcurrent 202 the array of photocells scanning area 41 detect indicia 192generating a signal at the input of constant current source 70 (FIG. 6)and resulting in fixture speed motor control 24 and wire feed motorcontrol 25 generating an output voltage over respective leads 153 (FIG.9). However, this voltage can not be applied to the wire feed motor 316and electrode travel motor 317 (FIG. 15) until relay contacts 326 and332, respectively, are closed. Relay contact 326 is controlled bycontrol relay 114 (FIG. 7) of the wire feed on-off control havingphotocell 106 scanning area 49 of the program while relay contact 332 iscontrolled by control relay 115 of the electrode travel on-off controlhaving photocell 107 scanning area 50 of the program. Thus, neither wirefeed nor fixture movement starts when indicia 192 is initially detected.

In the illustrated program during the first electrode rotation, 202 to203, about the work a first weld is made without the wire feed motorbeing energized. At point 202 photocell 107 (FIG. 7) detects indicia 195in area 50. As a result relay 115 is activated and contact 332 is closedso that electrode travel motor 317 is connected to a voltage source andstarts to operate. At point 203 the wire feed motor is programmed byindicia 194 to start operating and during the second pass around thework, 203 to 204, wire will be added to the weld. The current will bereduced at point 203 to account for the fact that the work hadpreviously been heated at the first pass. While two passes may beutilized as illustrated, it is clear that only a single pass may bedesirable. More specifically, after the first pass the current isreduced and the individual photocells 105 and 106 (FIG. 7) scanningareas 48 and 49 of the program detect the start of indicia 193 and 194,respectively. As a result control relays 113 and 114 are activated andrelay contact 326 (FIG. 15) is closed so that wire feed motor 316 isconnected to a voltage source and starts operation. In

addition, contact 322 is closed and, since contact 312 on control relay294 has already been closed by the application of a signal from thecycle start flip flop 290, the oscillator motor is energized to slowlyoscillate over a very small path the welding electrode. This smalloscillation has been found to materially improve the weld quality.

Welding of the pipe work piece started at point 202 with the electrodetravel motor initiation and stops when the indicia 194 in area 49terminates. At about this same time the weld current is rapidly reducedfrom its peak 204 at a rate consistent with good welding practices.

The program limit is indicated by the initial edge of indicia 196located in the program limit area 51. This area is scanned by photocell108, which through lead 116, applies a signal to the cycle controlcircuit 15 which results in the output 269 of the direction flip flop276 being grounded causing it to reverse direction. The output ofinverter 304 changes permitting the post purge delay 291 to operate.After a preselected amount of delay the output of the post purge delay291 changes, switching the cycle start flip flop 270 and de-energizingcontrol relay 294. This also switches the timer flip flop 300 therebyplacing all flip flops back in their original positions. At the sametime gate 280 gates the rapid pulse return generator 283 to the output263 of the time base logic circuit which drives the stepping motor 34backwards to return the carriage to the left hand starting position.

The foregoing description was directed to an embodiment of a programmeradapted for controlling a weld on a pipe made by an arc welder of theorbital type. While this embodiment was specific to a particular weldingoperation, it is clear from the description that other types of weldersor material handling systems may be used in conjunction with the programmer of the present invention. In addition, acetylene or other gaswelding apparatus could be used and gas mixtures and quantity controlledin place of current control in the preferred embodiment.

It is also apparent that the program or parts of it could be movedrelative to the scanner so that less surface area would have to be usedto illuminate the program sheet. It is also clear from the above examplethat a number of variations in program directed operation may be made.For example, wire feed may be increased or decreased during the programto allow for the welding of thicker or thinner work sections.Furthermore, the description of an orbital arc welder operation is onlyan example and all other types of welding may be accomplished utilizingthe programmer of the present invention. Thus, the programmer of thepresent invention could be utilized with one of the well-known weld pathguides, i.e., separate graphs or work edge monitoring, which arewellknown in the art for linear welding movements.

The present invention is not limited to the specific details of theparticular embodiments described, since many modifications will beapparent to those skilled in the art, the scope of the present inventionbeing limited only by the appended claims.

We claim:

1. A programming system for operating in a prescribed manner anautomatic welder having a fixture, a welding material feed and weld heatgenerating means comprising first means including a sheet program havinga plurality of indicia thereon for defining multiple operatingparameters for welding, second means for monitoring said program andgenerating signals representing said parameters, third means forcontrolling the feeding of weld material and the movement of the weldfixture, fourth means for controlling the generation of weld heat, saidthird and fourth means being responsive to said second means, and fifthmeans responsive to said signals generated by said second means and tosaid third means for controlling the monitoring of said second means.

2. The programming system of claim 1 wherein said first means includes aflexible sheet program having indicia representing changes in variousprocess parameters.

3. The programming system of claim 2 wherein said sheet is translucentand said indicia are opaque and wherein said second means includes aplurality of photocells for scanning a selected portion of said program,said photocells being responsive to said opaque indicia to generate saidsignal.

4. The programming system of claim 1 wherein said first means includesmeans for illuminating said program, said program being a flexible,removable, translucent sheet and said indicia being opaque elementscontained on said sheet, and wherein said second means includes meansfor scanning multiple selected portions of said sheet, said scanningmeans including a plurality of photocells for detecting the location ofa portion of said indicia on said sheet and generating a signal inresponse to said detection.

5. The programming system of claim 4 wherein one part of said scanningmeans and said program are moved relative to each other.

6. The programming system of claim 5 wherein said scanning meansincludes a fixed part having a plurality of fixed photocells fordetecting the presence of indicia on another part of said sheet.

7. The programming system of claim 1 wherein said second means includesscanning means for scanning selected portions of said program andwherein said scanning means has a fixed part and a movable part, saidmovable part including a plurality of photocells for detecting indiciaon one portion of said sheet program, said photocells being movedrelative to said sheet program, and wherein said fifth means controlssaid relative movement.

8. The programming system of claim 1 wherein said third means includes amotor regulator means responsive to said parameter signals forgenerating a plurality of regulating signals, said third means alsoincluding a plurality of motorized drive speed control means, each ofsaid control means being responsive to one of said regulating signals.

9. A programming system for operating in a prescribed manner a welderhaving a fixture, weld material feed and heat generating meanscomprising first means including a program sheet having indiciapositioned thereon to define multiple operating parameters for welding,second means for monitoring said program and the presence of saidindicia and generating operating signals responsive to the location ofsaid indicia on said program, said second means including scanning meansfor sequentially monitoring at least one area of said program sheet forindicia and generating at least one operating mode signal, said secondmeans also including fixed means for monitoring at least one other areaof said program sheet for indicia and generating at least one controlcondition signal, third means for controlling the feeding of weldmaterial to the weld fixture and for controlling the movement of theweld fixture responsive to said at least one operating mode signal,fourth means for controlling the weld heat generating means of thewelder in response to said at least one operating mode signal, and fifthmeans responsive to said fourth means and to at least one operatingcondition signal for controlling said second means.

10. The programming system of claim 9 wherein said scanning means has amovable carriage and includes a stepping motor for driving said carriageacross said at least one area, and wherein said fifth means includeslogic means for pulsing said stepping motor in a prescribed manner.

11. The programming system of claim 10 wherein said logic means includesa timing signal, means responsive to said timing signal and one of saidcontrol condition signals for generating a series of output pulses,stepping motor logic means responsive to said series of output pulsesand to a carriage direction control means for driving said steppingmotor in a predetermined direction and at a predetermined speed.

12. A programming system for operating a welder in a prescribed mannercomprising first means including a program having a plurality of indiciafor defining operating parameters, second means for scanning one portionof said indicia and. generating operating mode signals, third means formonitoring another portion of said indicia and generating operatingcondition signals, welding means including weld material feed means,weld fixture moving means and weld heat generating means, fourth meansresponsive to at least one of said mode signals for controlling saidweld heat generating means, fifth means responsive to at least one otherof said mode signals for controlling said feed means and sixth meansresponsive to at least one other mode signal for controlling said weldfixture moving means, and logic means for synchronizing the sequentialmonitoring of said second means in response to said operating mode andoperating condition signals.

13. A programming system of claim 12 wherein said sixth means includes apulse generator, and wherein said logic means includes a binary counterresponsive to said pulse generator and to a plurality of operating modesignals to generate an output signal, means responsive to said outputsignal for driving said second means.

14. A programming system for the automatic operation of an arc welderhaving a movable electrode, a wire feed source and a weld current sourceassociated with said electrode, comprising first means including aprogram having a plurality of indicia for defining operating parameters,second means including scanning means for monitoring the position of oneportion of said indicia and generating a plurality of operating modesignals dependent upon the indicia position, said mode signalsrepresenting programmed electrode travel, wire feed speed and weldcurrent variables, third means for monitoring another portion of saidindicia and generating a plurality of operating condition signalsrepresenting the range of values said mode signals may represent,fixture speed control means responsive to one of said mode signals formoving said electrode in a programmed manner, wire feed control meansresponsive to one of said mode signals for feeding wire to said weldelectrode in a programmed manner, and weld current control means forcontrolling the current supplied to said electrode in a programmedmanner, logic means including pulse generating means for generating aseries of pulses, stepping motor means for driving said scanning means,said logic means including means for applying said series of pulses tosaid stepping motor in any one of a plurality of modes to control thedirection and speed of said stepping motor operation.

15. The programming system of. claim 14 wherein said second meansincludes means for scanning a plurality of indicia containing areas, oneof said areas having indicia representing desired current variations asa function of electrode position, a second area representing variationin fixture speed and wire feed as a function of electrode position, anda third area having indicia representing on-off control of saidelectrode movement and said wire feed speed, said plurality of operatingmode signals including signals having values varying in accordance withthe changes in indicia in said first, second and third areas.

16. The programming system of claim 14 wherein said third means includesa plurality of indicia representing range selections for a plurality ofvariables including the said mode signal variables, said third meansincluding a plurality of detecting means responsive to said indicia forgenerating operating con dition signals.

17. The programming system of claim 12 wherein said scanning meansincludes a plurality of photocells supported on a carriage adapted to bemoved across said program by said stepping motor means.

18. The programming system of claim 12 wherein said third means includesa plurality of fixed photocells supported adjacent said program fordetecting said another portion of said indicia.

19. The programming system of claim 12 wherein said pulse generatingmeans generates a train of pulses in response to the energization ofsaid electrode travel speed control means by one of said operating modesignals, and wherein said logic means includes a binary counterresponsive to an operating condition signal for generating a series ofpulses, and stepping 18 said third and fourth means second means,

and fifth means responsive to said signals generated by said secondmeans and to said third means for controlling the monitoring of saidsecond means.

21. The programming system of claim 20, wherein said first meansincludes a flexible sheet program having indicia representing changes invarious process parameters.

22. The programming system of claim 21, wherein said sheet istranslucent and said indicia are opaque and wherein said second meansincludes a plurality of photocells for scanning a selected portion ofsaid program, said photocells being responsive to said opaque indicia togenerate said signal.

being responsive to said UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent NO. 3, 57,511 Dated pril 1 i97 l fl Robert Friedman eta1 It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

On the cover sheet [73] the name of the assignee should read NorthAmerican Rockwell Corporation Signed and sealed this 7th day of November1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O(10-69) USCOMM-DC 60376P69 U.S. GOVERNMENT PRINTING OFFICE I9550*366'334,

1. A programming system for operating in a prescribed manner anautomatic welder having a fixture, a welding material feed and weld heatgenerating means comprising first means including a sheet program havinga plurality of indicia thereon for defining multiple operatingparameters for welding, second means for monitoring said program andgenerating signals representing said parameters, third means forcontrolling the feeding of weld material and the movement of the weldfixture, fourth means for controlling the generation of weld heat, saidthird and fourth means being responsive to said second means, and fifthmeans responsive to said signals generated by said second means and tosaid third means for controlling the monitoring of said second means. 2.The programming system of claim 1 wherein said first means includes aflexible sheet program having indicia representing changes in variousprocess parameters.
 3. The programming system of claim 2 wherein saidsheet is translucent and said indicia are opaque and wherein said secondmeans includes a plurality of photocells for scanning a selected portionof said program, said photocells being responsive to said opaque indiciato generate said signal.
 4. The programming system of claim 1 whereinsaid first means includes means for illuminating said program, saidprogram being a flexible, removable, translucent sheet and said indiciabeing opaque elements contained on said sheet, and wherein said secondmeans includes means for scanning multiple selected portions of saidsheet, said scanning means including a plurality of photocells fordetecting the location of a portion of said indicia on said sheet andgenerating a signal in response to said detection.
 5. The programmingsystem of claim 4 wherein one part of said scanning means and saidprogram are moved relative to each other.
 6. The programming system ofclaim 5 wherein said scanning means includes a fixed part having aplurality of fixed photocells for detecting the presence of indicia onanother part of said sheet.
 7. The programming system of claim 1 whereinsaid second means includes scanning means for scanning selected portionsof said program and wherein said scanning means has a fixed part and amovable part, said movable part including a plurality of photocells fordetecting indicia on one portion of said sheet program, said photocellsbeing moved relative to said sheet program, and wherein said fifth meanscontrols said relative movement.
 8. The programming system of claim 1wherein said third means includes a motor regulator means responsive tosaid parameter signals for generating a plurality of regulating signals,said third means also including a plurality of motorized drive speedcontrol means, each of said control means being responsive to one ofsaid regulating signals.
 9. A programming system for operating in aprescribed manner a welder having a fixture, weld material feed and heatgenerating means comprising first means including a program sheet havingindicia positioned thereon to define multiple operating parameters forwelding, second means for monitoring said program and the presence ofsaid indicia and generating operating signals responsive to the locationof said indicia on said program, said second means including scanningmeans for sequentially monitoring at least one area of said programsheet for indicia and generating at least one operating mode signal,said second means also including fixed means for monitoring at least oneother area of said program sheet for indicia and generating at least onecontrol condition signal, third means for controlling the feeding ofweld material to the weld fixture and for contRolling the movement ofthe weld fixture responsive to said at least one operating mode signal,fourth means for controlling the weld heat generating means of thewelder in response to said at least one operating mode signal, and fifthmeans responsive to said fourth means and to at least one operatingcondition signal for controlling said second means.
 10. The programmingsystem of claim 9 wherein said scanning means has a movable carriage andincludes a stepping motor for driving said carriage across said at leastone area, and wherein said fifth means includes logic means for pulsingsaid stepping motor in a prescribed manner.
 11. The programming systemof claim 10 wherein said logic means includes a timing signal, meansresponsive to said timing signal and one of said control conditionsignals for generating a series of output pulses, stepping motor logicmeans responsive to said series of output pulses and to a carriagedirection control means for driving said stepping motor in apredetermined direction and at a predetermined speed.
 12. A programmingsystem for operating a welder in a prescribed manner comprising firstmeans including a program having a plurality of indicia for definingoperating parameters, second means for scanning one portion of saidindicia and generating operating mode signals, third means formonitoring another portion of said indicia and generating operatingcondition signals, welding means including weld material feed means,weld fixture moving means and weld heat generating means, fourth meansresponsive to at least one of said mode signals for controlling saidweld heat generating means, fifth means responsive to at least one otherof said mode signals for controlling said feed means and sixth meansresponsive to at least one other mode signal for controlling said weldfixture moving means, and logic means for synchronizing the sequentialmonitoring of said second means in response to said operating mode andoperating condition signals.
 13. A programming system of claim 12wherein said sixth means includes a pulse generator, and wherein saidlogic means includes a binary counter responsive to said pulse generatorand to a plurality of operating mode signals to generate an outputsignal, means responsive to said output signal for driving said secondmeans.
 14. A programming system for the automatic operation of an arcwelder having a movable electrode, a wire feed source and a weld currentsource associated with said electrode, comprising first means includinga program having a plurality of indicia for defining operatingparameters, second means including scanning means for monitoring theposition of one portion of said indicia and generating a plurality ofoperating mode signals dependent upon the indicia position, said modesignals representing programmed electrode travel, wire feed speed andweld current variables, third means for monitoring another portion ofsaid indicia and generating a plurality of operating condition signalsrepresenting the range of values said mode signals may represent,fixture speed control means responsive to one of said mode signals formoving said electrode in a programmed manner, wire feed control meansresponsive to one of said mode signals for feeding wire to said weldelectrode in a programmed manner, and weld current control means forcontrolling the current supplied to said electrode in a programmedmanner, logic means including pulse generating means for generating aseries of pulses, stepping motor means for driving said scanning means,said logic means including means for applying said series of pulses tosaid stepping motor in any one of a plurality of modes to control thedirection and speed of said stepping motor operation.
 15. Theprogramming system of claim 14 wherein said second means includes meansfor scanning a plurality of indicia containing areas, one of said areashaving indicia representing desired current variations as a function ofelectrode position, a secOnd area representing variation in fixturespeed and wire feed as a function of electrode position, and a thirdarea having indicia representing on-off control of said electrodemovement and said wire feed speed, said plurality of operating modesignals including signals having values varying in accordance with thechanges in indicia in said first, second and third areas.
 16. Theprogramming system of claim 14 wherein said third means includes aplurality of indicia representing range selections for a plurality ofvariables including the said mode signal variables, said third meansincluding a plurality of detecting means responsive to said indicia forgenerating operating condition signals.
 17. The programming system ofclaim 12 wherein said scanning means includes a plurality of photocellssupported on a carriage adapted to be moved across said program by saidstepping motor means.
 18. The programming system of claim 12 whereinsaid third means includes a plurality of fixed photocells supportedadjacent said program for detecting said another portion of saidindicia.
 19. The programming system of claim 12 wherein said pulsegenerating means generates a train of pulses in response to theenergization of said electrode travel speed control means by one of saidoperating mode signals, and wherein said logic means includes a binarycounter responsive to an operating condition signal for generating aseries of pulses, and stepping motor logic means responsive to saidseries of pulses and a plurality of operating signals for driving saidstepping motor means.
 20. A programming system for operating in aprescribed manner an automatic welder having a fixture and weld heatgenerating means comprising: first means including a sheet programhaving a plurality of indicia thereon for defining multiple operatingparameters for welding, second means for monitoring said program andgenerating signals representing said parameters, third means forcontrolling the movement of the weld fixture, fourth means forcontrolling the generation of weld heat, said third and fourth meansbeing responsive to said second means, and fifth means responsive tosaid signals generated by said second means and to said third means forcontrolling the monitoring of said second means.
 21. The programmingsystem of claim 20, wherein said first means includes a flexible sheetprogram having indicia representing changes in various processparameters.
 22. The programming system of claim 21, wherein said sheetis translucent and said indicia are opaque and wherein said second meansincludes a plurality of photocells for scanning a selected portion ofsaid program, said photocells being responsive to said opaque indicia togenerate said signal.